#7 Visualization framework

[vowitaf]

Create a visualization framework that lets end-users and developers tie in
visualizations into the ivcsf in a much more useful way. Here's an initial
list of what this might do:

- Uniform user interface to user and programming interface to
visualization algorithms.
- This should allow any visualization algorithm to define a mapping
between its control and predefined actions. The result is for example that
zooming is always achieved using rightclick+drag, etc.
-- Allow modifying interaction mapping in ivcsf preferences.
- Create pipes between data analysis and visualization.
- Allow visualizations to register themselves to receive updates from
other algorithms and update their viz.
-- Provide smart caching for this purpose.